Optical disk substrate and lightguide plate

ABSTRACT

An optical disk substrate and a light guide plate which are formed from a resin composition comprising 0.1 to 20 parts by weight of compound represented by the following formula (I):  
                 
based on 100 parts by weight of polycarbonate resin. There can be provided an optical disk substrate formed from the resin composition of the present invention, particularly an optical disk substrate which allows the shape of a stamper to be transferred thereon with high precision and hardly undergoes warpage caused by environmental changes as a high density recording medium, and a light guide plate which has little uneven brightness and hardly undergoes warpage.

TECHNICAL FIELD

The present invention relates to a polycarbonate resin compositionhaving precise transferability to the shape of a stamper, high rigidity,low water absorbability and transparency and to an optical disksubstrate and an optical disk which are obtained from the composition.More specifically, it relates to an optical disk substrate and anoptical disk such as CD (Compact Disk), MD (Magnet-Optical Disk) and DVD(Digital Versatile Disk) which have precise transferability and hardlyundergo warpage caused by environmental changes. In particular, thepresent invention relates to a substrate for a high density optical diskhaving a very large recording capacity.

Further, the present invention relates to an light guide plate used inplanar light equipment attached to a display such as a liquid crystaldisplay.

BACKGROUND ART

The recording densities of optical disks have been increasing from 0.6GB of CD to 4.7 GB of DVD. However, along with progress in informationtechnology, the development of an optical disk market is remarkable, andthe emergence of a high density optical disk capable of storing a largeramount of data is desired. For example, an optical disk with a recordingdensity of 100 Gbit/inch² or higher which can accommodate to digitalbroadcasting is desired.

To increase the density of an optical disk, a distance between groovesor pits, i.e., a track pitch, is narrowed, thereby increasing arecording density in a track direction.

For example, an increase in recording density from CD to DVD has beenachieved by narrowing the track pitch from 1.6 μm to 0.74 μm.

An optical disk substrate is produced by injection-molding(injection-compression-molding) a thermoplastic resin. At that time,fine pits and projections formed in advance on a stamper attached to amold and corresponding to recording/reproduction signals are transferredonto the surface of the substrate from the stamper. Thus, at the time ofmolding the substrate, transferring the pits and projections of thestamper with high precision, i.e., precise transferability, isimportant. Particularly, in molding a high density optical disksubstrate, the precise transferability is very important.

For high density optical disks, it is important to comprise a substratewith high transferability. In addition to this, it is also important toundergo smaller warpage of a substrate and smaller warpage with respectto environmental changes than conventional optical disks, due to thefollowing reason. That is, along with an increase in density, thewavelength of laser is made shorter and the NA of pickup lens is madehigher, so that even very small warpage of a substrate results in alarge coma aberration, thereby causing a focus error or a trackingerror. Further, since the pickup lens and the substrate become closer toeach other due to the increase in NA, it is important that the warpageof the substrate and the warpage caused by environmental changes aresmall, so as to prevent the lens and the substrate from making contactwith each other.

Heretofore, a polycarbonate resin has been used as a material ofsubstrates for optical disks such as CD (Compact Disk), MO(Magnetooptical Disk) and DVD (Digital Versatile Disk) due to itsexcellent transparency, heat resistance, mechanical properties anddimensional stability.

However, along with an increase in the recording densities of theoptical disks, optical disk substrates made of the polycarbonate resinhave been becoming unsatisfactory in view of precise transferability andwarpage.

To meet demand for an improvement in transferability, a variety ofstudies have heretofore been made in terms of both molding techniquesand material modification. As for the former, for example, it has beenconfirmed that a method of setting a cylinder temperature and a moldtemperature at the time of substrate molding at high temperatures iseffective. However, this method requires long cooling time in a moldbecause it is high temperature molding, thereby extending a moldingcycle and resulting in low productivity. If molding is forcibly carriedout in a high cycle, improper mold release occurs when a substrate isreleased from a mold, thereby resulting in deformed pits or grooves andlowering precision of transfer. As for the latter, for example, a method(JP-A 9-208684 (the term “JP-A” as used herein means an “unexaminedpublished Japanese patent application”) and JP-A 11-1551, for example)comprising incorporating a large amount of a low molecular weightcompound in a polycarbonate resin so as to impart high flowability or amethod (JP-A 11-269260, for example) comprising using a specific longchain alkyl phenol as a terminal blocking agent is proposed. However, inthe method of increasing the content of the low molecular weightcompound or the method of modifying terminal groups by the long chainalkyl phenol, deterioration in thermal stability is generallyremarkable. Therefore, as a result of promoting thermal decomposition atthe time of molding, the mechanical strength of a disk substrate issignificantly degraded, so that the substrate is cracked by force whichpushes the substrate out of a mold or the substrate is broken duringhandling of the optical disk substrate.

Further, to improve transfer of pits and projections to the surface of apolycarbonate resin and warpage, a resin composition containing abiphenyl compound or a terphenyl compound (particularly anorthoterphenyl compound or a metaterphenyl compound) in a given amountis proposed (JP-A 2000-239513). When this resin composition contains thebiphenyl compound, the amount of deposits on a mold is large, resultingin low productivity, while when the composition contains the terphenylcompound, transferability is not improved to a fully satisfactory level.

Thus, the prior arts are intended to improve transferability byimproving the flowability of the resin. However, they fail to providepracticable substrates at high efficiency.

Meanwhile, to meet demand for an improvement in warpage as well, avariety of studies have been made in terms of both molding techniquesand material modification. As for the former, although warpage of asubstrate can be kept small by finely controlling molding conditions, itis difficult to transfer the shape of a stamper precisely. As for thelatter, it is known to be effective to use a rigid material having ahigh flexural or tensile modulus. Thus, for the purpose of improving therigidity of a polycarbonate resin, a method of adding such additives asglass fibers and a filler has been attempted. However, although theabove additives improve the rigidity of the polycarbonate resin, theyare exposed to the surface, thereby degrading precision of transfer.

“Precise transferability” in the present invention refers to acharacteristic that fine pits and projections formed on a stamper can betransferred precisely when an optical disk substrate is produced from athermoplastic resin molding material by injection molding.

As for warpage with respect to environmental changes, JP-A 2000-11449proposes “a disk-shaped data recording medium which comprises asubstrate, a recording layer disposed on the substrate so as to recorddata signals and a transparent protective layer laminated on therecording layer and on which data signals are recorded/reproduced bylight entering from the transparent protective layer side, the substratecomprising a resin core layer and a resin surface layer which isintegrated with the core layer, has pits and projections correspondingto data signals of the recording layer side on one surface and hashigher flowability than the core layer, the surface layer of thesubstrate being made of a resin having a water absorption of not higherthan 0.3%″, so as to inhibit deformation caused by absorption of water,and suggests a complex substrate configuration by coinjection molding orsandwich molding so as to solve the problem.

Meanwhile, a light guide plate is an optical member used in planar lightequipment attached to various displays such as a liquid crystal display.In an edge light mode, the light guide plate serves to allow light froma light source to eject in a direction perpendicular to the injectiondirection. Further, on the surface of the light guide plate, fine pitsand projections which reflect or refract light efficiently are formed.Since such a light guide plate serves as a light source of a display,the member must have high permeability so as to achieve high brightnessand uneven brightness on the light emitting surface must be low so as toachieve a uniform outgoing light quantity.

In recent years, as the size and thickness of displays have beenincreasing and decreasing year by year, respectively, the light guideplate has also been shifted to a larger size and a smaller thickness.When the light guide plate is produced by an injection molding method,the distance between the gate and the end of flow becomes longer alongwith an increase in size, so that pressure does not work effectively atthe end of the flow. Further, along with a decrease in thickness, theprogression of solidification of a molten resin by cooling isaccelerated, so that pressure does not work effectively at the end offlow as in the case of the increase in size. Thus, there occurs aproblem that transferability of pits and projections at the end of theflow is poor.

Meanwhile, displays such as a liquid crystal display are increasinglyused in the outdoor. In this case, light guide plates are warped by achange in humidity of surrounding, thereby causing uneven display orinterference with other components.

DISCLOSURE OF THE INVENTION

A first object of the present invention is to provide a polycarbonateresin composition having precise transferability to the shape of astamper, high rigidity, low water absorbability and transparency and anoptical disk substrate and an optical disk which are obtained from thecomposition, have high transferability and are hardly warped,particularly a high density optical disk substrate.

A second object of the present invention is to provide a light guideplate which shows little uneven brightness, is hardly deformed byabsorption of water during use and can be made larger and thinner insize.

Means for Solving the Problems

According to studies made by the present inventors, it has been foundthat the first object of the present invention is achieved by an opticaldisk substrate formed from a resin composition comprising 0.1 to 20parts by weight of compound represented by the following formula (I):

wherein X represents:

-   R¹ and R² independently represent a hydrogen atom, a halogen atom,    an alkyl group or an alkoxy group having 1 to 8 carbon atoms, n and    m independently represent an integer of 1 to 3, and Q¹ and Q²    independently represent a hydrogen atom, a chlorine atom, a bromine    atom, a cyano group or an alkyl group having 1 to 8 carbon atoms,    based on 100 parts by weight of polycarbonate resin.

Further, according to the studies made by the present inventors, it hasbeen found that the second object of the present invention is achievedby a light guide plate formed from a resin composition comprising 0.1 to20 parts by weight of compound represented by the above formula (I)based on 100 parts by weight of polycarbonate resin.

The above optical disk substrate and light guide plate which are theobjects of the present invention have fines pits and projections foroptical recording or light scattering on surfaces thereof. By meltinjection molding the resin composition of the present invention, moldedarticles having fine pits and projections on surfaces thereof can beobtained easily. In addition, the obtained molded articles haveexcellent physical properties and optical properties.

Hereinafter, the optical disk substrate and light guide plate of thepresent invention will be further described.

The optical disk substrate and light guide plate of the presentinvention use a polycarbonate resin as a resin. The polycarbonate resinis generally obtained by reacting a dihydric phenol with a carbonateprecursor by an interfacial polymerization method or a meltpolymerization method. Representative examples of the dihydric phenolinclude

-   hydroquinone, resorcinol, 4,4′-dihydroxydiphenyl,-   bis(4-hydroxyphenyl)methane,-   bis{(4-hydroxy-3,5-dimethyl)phenyl}methane,-   1,1-bis(4-hydroxyphenyl)ethane,-   1,1-bis(4-hydroxyphenyl)-1-phenylethane,-   2,2-bis(4-hydroxyphenyl)propane (bisphenol A),-   2,2-bis{(4-hydroxy-3-methyl)phenyl}propane,-   2,2-bis{(4-hydroxy-3,5-dimethyl)phenyl}propane,-   2,2-bis{(3,5-dibromo-4-hydroxy)phenyl}propane,-   2,2-bis{(3-isopropyl-3-hydroxy)phenyl}propane,-   2,2-bis{(4-hydroxy-3-phenyl)phenyl}propane,-   2,2-bis(4-hydroxyphenyl)butane,-   2,2-bis(4-hydroxyphenyl)-3-methylbutane,-   2,2-bis(4-hydroxyphenyl)-3,3-dimethylbutane,-   2,4-bis(4-hydroxyphenyl)-2-methylbutane,-   2,2-bis(4-hydroxyphenyl)pentane,-   1,1-bis(4-hydroxyphenyl)cyclohexane,-   1,1-bis(4-hydroxyphenyl)-4-isopropyl cyclohexane,-   1,1-bis(4-hydroxyphenyl)-3,3,5-trimethyl cyclohexane,-   9,9-bis(4-hydroxyphenyl)fluorene,-   9,9-bis{(4-hydroxy-3-methyl)phenyl}fluorene,-   1,1′-bis(4-hydroxyphenyl)-ortho-diisopropyl benzene,-   1,1′-bis(4-hydroxyphenyl)-meta-diisopropyl benzene,-   1,1′-bis(4-hydroxyphenyl)-para-diisopropyl benzene,-   1,3-bis(4-hydroxyphenyl)-5,7-dimethyl adamantane,-   4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl sulfoxide,    4,4′-dihydroxydiphenyl sulfide,-   4,4′-dihydroxydiphenyl ketone, 4,4′-dihydroxydiphenyl-   ether, 4,4′-dihydroxydiphenyl ester,-   1,1-bis(4-hydroxyphenyl)-2-methylpropane,-   1,1-bis(4-hydroxyphenyl)-2-ethylhexane, and-   2,2-bis(4-hydroxyphenyl)-2-methylpentane. These may be used alone or    in combination of two or more.

Of these, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A),1,1-bis(4-hydroxyphenyl)-2-methylpropane and2,2-bis(4-hydroxyphenyl)-4-methylpentane are preferred, and2,2-bis(4-hydroxyphenyl)propane is particularly preferred.

Illustrative examples of the carbonate precursor used in producing thepolycarbonate by use of the dihydric phenol include a carbonyl halide, acarbonate ester and a haloformate. Specific examples thereof includephosgene, diphenyl carbonate and dihaloformate of dihydric phenol. Ofthese, phosgene and diphenyl carbonate are preferred.

When the above dihydric phenol and carbonate precursor are reacted witheach other by a method such as a solution polymerization method or amelt polymerization method so as to produce the polycarbonate resin, acatalyst, a terminal blocking agent and an antioxidant for the dihydricphenol may be used as required.

A reaction by the interfacial polymerization method is generally areaction between a dihydric phenol and phosgene and is carried out inthe presence of an acid binder and an organic solvent. As the acidbinder, an alkali metal oxide such as sodium hydroxide or potassiumhydroxide or an amine compound such as pyridine is used, for example. Asthe organic solvent, a halogenated hydrocarbon such as methylenechloride or chlorobenzene is used, for example. Further, a catalyst suchas a tertiary amine, a quaternary ammonium compound or a quaternaryphosphonium compound, e.g., triethylamine, tetra-n-butyl ammoniumbromide and tetra-n-butyl phosphonium bromide, can be used so as toaccelerate the reaction. In that case, it is preferable that thereaction temperature be generally 0 to 40° C., that the reaction time beabout 10 minutes to 5 hours and that the pH during the reaction be keptat 9 or higher.

Further, in the polymerization reaction, a terminal blocking agent isgenerally used. As the terminal blocking agent, a monofunctional phenolcan be used. The monofunctional phenol is generally used as a terminalblocking agent so as to control a molecular weight, and since apolycarbonate resin obtained by use of the monofunctional phenol has itsterminals blocked by groups based on the monofunctional phenol, it hasbetter thermal stability than a polycarbonate resin obtained withoutusing the monofunctional phenol. An example of the monofunctional phenolis a monofunctional phenol which is generally phenol or a lower alkylsubstituted phenol and is represented by the following formula [II]:

[wherein A is a hydrogen atom or a linear or branched alkyl or phenylsubstituted alkyl group having 1 to 9 carbon atoms, and r is an integerof 1 to 5, preferably 1 to 3.]

Specific examples of the above monofunctional phenol include phenol,p-t-butyl phenol, p-cumyl phenol and isooctyl phenol.

Further, as other monofunctional phenols, phenols or benzoic acidchlorides having a long chain alkyl group or aliphatic ester group as asubstituent or long chain alkyl carboxyl chlorides can be used. Whenthey are used to block the terminals of a polycarbonate polymer, theynot only act as a terminal blocking agent or a molecular weight modifierbut also improve the melt flowability of the resin so as to facilitatemoldability. In addition, they have an effect of lowering physicalproperties as a substrate, particularly the water absorption of theresin, and an effect of reducing the birefringence of the substrate.Hence, they are preferably used. In particular, phenols which have along chain alkyl group as a substituent and are represented by thefollowing formulae [III] and [IV] are preferably used.

[In the above formulae, X is —R—CO—O— or —R—O—CO— wherein R is a singlebond or a divalent aliphatic hydrocarbon group having 1 to 10,preferably 1 to 5 carbon atoms, and n is an integer of 10 to 50.]

As the substituted phenol of the above formula (III), a substitutedphenol in which n is 10 to 30 is preferred, and a substituted phenol inwhich n is 10 to 26 is particularly preferred. Specific examples thereofinclude decyl phenol, dodecyl phenol, tetradecyl phenol, hexadecylphenol, octadecyl phenol, eicosyl phenol, docosyl phenol and triacontylphenol.

Further, as the substituted phenol of the above formula (IV), a compoundin which X is —R—CO—O— and R is a single bond is appropriate, and acompound in which n is 10 to 30, particularly 10 to 26, is suitable.Specific examples thereof include decyl hydroxybenzoate, dodecylhydroxybenzoate, tetradecyl hydroxybenzoate, hexadecyl hydroxybenzoate,eicosyl hydroxybenzoate, docosyl hydroxybenzoate and triacontylhydroxybenzoate.

These terminal blocking agents are desirably introduced into at least 5mol %, preferably at least 10 mol %, of all terminals of the obtainedpolycarbonate resin. Further, the terminal blocking agents may be usedalone or in admixture of two or more.

A representative reaction by the melt polymerization method is generallyan ester exchange reaction between a dihydric phenol and a carbonateester and is carried out by a method in which the dihydric phenol andthe carbonate ester are mixed together under heating in the presence ofan inert gas and an alcohol or phenol produced is distilled out.Although the reaction temperature varies depending on the boiling pointof the alcohol or phenol produced, it generally ranges from 120° C. to350° C. In the late stage of the reaction, the reaction system isreduced to about 10 to 0.1 Torr (1,300 to 13 Pa) so as to facilitatedistill-out of the alcohol or phenol produced. The reaction time isgenerally about 1 to 4 hours.

As the carbonate ester, an ester of an aryl group having 6 to 10 carbonatoms, aralkyl group or alkyl group having 1 to 4 carbon atoms which mayhave a substituent may be used. Specific examples thereof includediphenyl carbonate, ditolyl carbonate, bis(chlorophenyl)carbonate,m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl)carbonate,dimethyl carbonate, diethyl carbonate and dibutyl carbonate. Of these,diphenyl carbonate is preferred.

Further, to increase the polymerization rate, a polymerization catalystcan be used. As the polymerization catalyst, catalysts which aregenerally used in an esterification reaction and an ester exchangereaction, such as alkali metal compounds, e.g., sodium hydroxide,potassium hydroxide and sodium and potassium salts of dihydric phenol;alkaline earth metal compounds, e.g., calcium hydroxide, bariumhydroxide and magnesium hydroxide; nitrogen-containing basic compounds,e.g., tetramethylammonium hydroxide, tetraethylammonium hydroxide,trimethylamine and triethylamine; alkoxides of alkali metals andalkaline earth metals; organic acid salts of alkali metals and alkalineearth metals; zinc compounds, boron compounds, aluminum compounds,silicon compounds, germanium compounds, organotin compounds, leadcompounds, osmium compounds, antimony compounds, manganese compounds,titanium compounds and zirconium compounds can be used. These catalystsmay be used alone or in combination of two or more. These polymerizationcatalysts preferably are used in an amount of 1×10⁻⁸ to 1×10⁻³equivalents, more preferably 1×10⁻⁷ to 5×10⁻⁴ equivalents, per mole ofthe dihydric phenol which is a raw material.

Further, in the polymerization reaction, to reduce phenolic terminalgroups, a compound such as bis(chlorophenyl)carbonate,bis(bromophenyl)carbonate, bis(nitrophenyl)carbonate,bis(phenylphenyl)carbonate, chlorophenylphenyl carbonate,bromophenylphenyl carbonate, nitrophenylphenyl carbonate, phenylphenylcarbonate, methoxycarbonylphenylphenyl carbonate orethoxycarbonylphenylphenyl carbonate is preferably added in the latestage or after completion of the polycondensation reaction. Of these,2-chlorophenylphenyl carbonate, 2-methoxycarbonylphenylphenyl carbonateand 2-ethoxycarbonylphenylphenyl carbonate are preferably used, and2-methoxycarbonylphenylphenyl carbonate is particularly preferably used.

The viscosity average molecular weight of the polycarbonate resin ispreferably within a range of 10,000 to 30,000, more preferably 12,000 to20,000. A polycarbonate resin optical molding material having theviscosity average molecular weight is preferred since it hassatisfactory strength as an optical material and has good meltflowability at the time of molding so that no molding distortion occurs.When the molecular weight is excessively low, the strength of a moldedsubstrate is not satisfactory, while when it is excessively high, meltflowability at the time of molding is poor, and an undesirable opticaldistortion increases in the substrate.

After the polycarbonate resin as a raw material is produced by aconventionally known method (such as a solution polymerization method ora melt polymerization method), it is preferably filtered in a solutionstate so as to remove impurities such as unreacted components andforeign matter.

The resin composition constituting the optical disk substrate or thelight guide plate in the present invention is produced by adding aspecific amount of a compound (hereinafter may be abbreviated simply as“additive compound”) represented by the following formula (I) to theabove polycarbonate resin.

Next, this additive compound will be further described.

The additive compound of the present invention, as shown by the aboveformula (I), is a compound comprising two benzene rings bonded to eachother via X which is a divalent group represented by the followingformulae.

In the above formula (I), R¹ and R² each are a substituent or atombonded to the benzene ring and independently represent a hydrogen atom,a halogen atom, an alkyl group or an alkoxy group having 1 to 8 carbonatoms, n and m independently represent an integer of 1 to 3, preferably1, and Q¹ and Q² independently represent a hydrogen atom, a chlorineatom, a bromine atom, a cyano group or an alkyl group having 1 to 8carbon atoms.

In the above formula (I), R¹ and R² are preferably a hydrogen atom, analkyl group having 1 to 8 carbon atoms or an alkoxy group, particularlypreferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.Further, Q¹ and Q² are preferably a hydrogen atom or an alkyl grouphaving 1 to 8 carbon atoms, particularly preferably a hydrogen atom oran alkyl group having 1 to 3 carbon atoms.

In the above formula (I), X is preferably one of the following groups.

Compounds having the leftmost group, the middle group and the rightmostgroup are referred to as a stilbene compound, a diphenyl carbonatecompound and a phenyl benzoate compound, respectively. Of these, themost preferable compound is the stilbene compound whose X is representedby the following formula.

Specific examples of the stilbene compound include stilbene (Q¹ and Q²are a hydrogen atom) and 4,4′-dimethyl stilbene (R¹ and R² are a methylgroup).

Of the above additive compounds, a resin composition containing thestilbene compound whose X is represented by the following formula:

has advantages that it has excellent transferability and that a moldedarticle obtained from the composition has a very good flexural modulusand very low water absorption.

Meanwhile, a resin composition containing the diphenyl carbonatecompound whose X is a carbonate bond or the phenyl benzoate compoundwhose X is an ester bond has improved transferability, and a moldedarticle obtained from the composition has balanced properties as awhole, as exemplified by a good flexural modulus and low waterabsorption.

A resin composition containing a diphenyl ether compound whose X is —O—has excellent transferability, and a molded article obtained from thecomposition shows low water absorption and a slightly improved flexuralmodulus. A resin composition containing a diphenyl sulfone compound orphenylsulfonic acid phenyl ester compound whose X is

has slightly improved transferability, and a molded article obtainedfrom the composition has improved heat resistance and an improvedflexural modulus.

A resin composition containing a benzophenone compound or benzylcompound whose X is —CO— or

has very good transferability but it also has a low glass transitionpoint. Further, a molded article obtained from the composition hasimproved water absorption and an improved flexural modulus.

The resin composition of the present invention contains the additivecompound represented by the above formula (I) in an amount of 0.1 to 20parts by weight, preferably 0.5 to 10 parts by weight, based on 100parts by weight of the polycarbonate resin. The resin composition mostpreferably contains the additive compound in an amount of 1 to 8 partsby weight.

The resin composition of the present invention is prepared by use of anymethod. For example, a method which comprises mixing the above additivecompound into the polycarbonate resin in a solution state, distillingout a solvent and then melt-pelletizing the resulting mixture by avented extruder or the like or a method comprising mixing thepolycarbonate resin with the above additive compound by use of a supermixer, a tumbler, a Nauta mixer or the like and pelletizing the mixtureby use of a twin screw extruder or the like. Further, if necessary,additives such as a stabilizer, an antioxidant, a light stabilizer, acolorant, a lubricant and a mold release agent can be added. Further, inthe extrusion step (pelletizing step) of obtaining a pellet-shapedpolycarbonate resin composition to be injection-molded, the compositionis preferably passed through a sintered metal filter having a filtrationaccuracy of 10 μm during melt stage so as to remove foreign mattertherefrom. If necessary, an additive such as a phosphorus basedantioxidant is preferably added. In any event, it is necessary tominimize the contents of foreign matter, impurities and solvents in theraw material resin composition before injection molding.

To produce an optical disk substrate from the above polycarbonate resincomposition, an injection molding machine (including an injectioncompression molding machine) is employed. As the injection moldingmachine, a generally used machine may be used. However, an injectionmolding machine whose cylinder and screws show low adhesion to the resinand which is made of a material showing corrosion resistance andabrasion resistance is preferably used so as to inhibit the occurrenceof carbides and to increase the reliability of the disk substrate. Asfor conditions for injection molding, a cylinder temperature of 300 to400° C. and a mold temperature of 50 to 140° C. are preferred. By theseconditions, an optically excellent optical disk substrate can beobtained. The atmosphere in the molding step is preferably as clean aspossible in consideration of the objects of the present invention.Further, it is important to fully dry the material to be molded so as toremove water therefrom and also important to be careful not to allowretention which may cause decomposition of the molten resin.

The thus molded optical disk substrate is suitably used as a substratenot only for current optical disks such as a compact disk (CD), amagnetooptical disk (MO) and DVD but also for high density optical disksas typified by a Blu-ray Disc (BD) on which recording and reproductionare conducted via a 0.1-mm-thick transparent cover layer placed on thedisk substrate.

Since the polycarbonate resin optical molding material of the presentinvention has high precision transferability, an optical disk substratehaving a distance between grooves or pits of 0.1 to 0.8 μm, preferably0.1 to 0.5 μm, more preferably 0.1 to 0.35 μm, can be obtained easily bymolding. Further, an optical disk substrate whose groove or pit has anoptical depth of λ/8n to λ/2n, preferably λ/6n to λ/2n, more preferablyλ/4n to λ/2n wherein λ is the wavelength of laser light used forrecording and reproduction and n is the refractive index of thesubstrate can be obtained. Thus, a substrate for a high density opticaldisk recording medium having a recording density of 100 Gbit/inch² orhigher can be provided easily.

When a light guide plate is produced from the polycarbonate resincomposition of the present invention, a method comprising molding thecomposition into a flat plate by a known extrusion method or flowcasting method and then forming pits and projections on a surface of theplate or a method comprising producing the light guide plate by aninjection molding method by use of a mold having a cavity in which pitsand projections are formed can be used. In particular, the injectionmolding method is preferred from the viewpoint of productivity.

A molding machine used in the injection molding method may be agenerally used molding machine. However, a molding machine whosecylinder and screws show low adhesion to the resin and which is made ofa material showing corrosion resistance and abrasion resistance ispreferably used so as to inhibit the occurrence of carbides and toincrease the reliability of the light guide plate. The atmosphere in themolding step is preferably as clean as possible in consideration of theobjects of the present invention. Further, it is important to fully drythe material to be molded so as to remove water therefrom and alsoimportant to be careful not to allow retention which may causedecomposition of the molten resin.

The thus molded light guide plate is suitably used as a light guideplate not only for small displays such as a liquid crystal display for apotable telephone but also for large liquid crystal displays of 14inches or larger.

BRIEF DESCRIPTIONS OF THE INVENTION

FIG. 1 shows the sizes and shapes in a cross section of pits andprojections on the surface of a light guide plate.

EXAMPLES

Hereinafter, the present invention will be further described withreference to Examples. The present invention shall not be limited bythese Examples in any way as long as the spirit of the present inventionis upheld. “Parts” in Examples and Comparative Examples refers to partsby weight. Evaluations were made in accordance with the followingmethods.

(1) Viscosity Average Molecular Weight

A specific viscosity (ηsp) obtained by use of a 20° C. solution preparedby dissolving 0.7 g of polycarbonate resin in 100 mL of methylenechloride is substituted into the following expression so as to determinea viscosity average molecular weight.ηsp/c=[η]+0.45×[η]² c ([η] is a limiting viscosity.)

-   [η]=1.23×10⁻⁴M^(0.83)-   c=0.7    (2) Glass Transition Temperature

A glass transition temperature is measured in a nitrogen atmosphere(nitrogen flow rate: 40 ml/min) at a temperature increasing rate of 20°C./min by use of the thermal analysis system DSC-2910 of TA InstrumentsCo., Ltd.

(3) Water Absorption

In accordance with ASTM D-570, a φ45-mm molded plate is immersed inwater, and water absorption is determined from a rate of change inweight (% by weight).

(4) Flexural Modulus

A flexural modulus is measured in accordance with ASTM D-790.

(5) Transferability

An optical disk substrate having a diameter of 120 mm and a thickness of1.2 mm is molded by use of the injection molding machine MO40D-3H ofNissei Plastic Industrial Co., Ltd. and a stamper on which grooves eachhaving a depth of 200 nm and a width of 0.2 μm are engraved at aninterval of 0.5 μm. The cylinder temperature and the mold clamping forceare fixed at 360° C. and 40 tons, respectively, and the mold temperatureis set for each resin as shown in Table 1.

The depths of grooves transferred from the stamper onto the abovesubstrate are measured on 5 spots on a radius of 40 mm by use of anatomic force microscope (SPI3700 of Seiko Instruments Inc.).Transferability is expressed as a transfer rate represented by thefollowing expression. The larger the value, the better thetransferability is transfer rate (%)=100×(depth of groove ofdisk)/(depth of groove of stamper).

(6) Initial Mechanical Property (Initial R-Tilt)

An optical disk substrate having a diameter of 120 mm and a thickness of1.2 mm is molded by use of the injection molding machine MO40D-3H ofNissei Plastic Industrial Co., Ltd. Then, on the signal surface side ofthe disk substrate obtained by injection molding, a reflection film, adielectric layer 1, a phase change recording film and a dielectric layer2 are deposited by sputtering, and a thin polycarbonate film cover layeris laminated thereon so as to prepare an optical disk. Then, a spacer isinserted between the disks so as to prevent the disks from contactingeach other, and the disks are left to stand at a temperature of 23° C.and a humidity of 50% RH for at least two days. Tilt is evaluated by useof the three-dimensional shape measuring instrument DLD-3000U of JapanEM Co., Ltd. when a change in the Tilt with respect to thermalcontraction and environmental changes is settled, and the Tilt is takenas an initial mechanical property.

(7) Maximum Value of Curvature Deformation (ΔR-Tiltmax)

After a substrate whose initial mechanical property has been evaluatedis left to stand in constant-temperature constant-humidity equipmentwhose temperature is 30° C. and humidity is 90% RH for 72 hours, thedisk is transferred to an environment whose temperature is 23° C. andhumidity is 50% RH, and the maximum value (ΔR-Tiltmax) of curvaturedeformation of the disk is then evaluated by the three-dimensional shapemeasuring instrument DLD-3000U of Japan EM Co., Ltd.

(8) Test for Measuring Quantity of Deposits

3,000 optical disk substrates each having a diameter of 120 mm and athickness of 1.2 mm are molded continuously by use of the injectionmolding machine MO40D-3H of Nissei Plastic Industrial Co., Ltd. and astamper on which grooves each having a depth of 200 nm and a width of0.2 μm are engraved at an interval of 0.5 μm. After continuous moldingof the 3,000 substrates, deposits on the stamper after molding areextracted by chloroform and dried, and the quantity of the deposits ismeasured.

The quantity of the deposits is evaluated based on the followingcriteria.

-   A: The quantity of deposits after molding of 3,000 substrates is 1    to 10 mg.-   B: The quantity of deposits after molding of 3,000 substrates is 11    to 20 mg.-   C: The quantity of deposits after molding of 3,000 substrates is 21    mg or higher.-   D: Deposits are transferred to substrates before molding of 3,000    substrates is completed.    (9) Uneven Brightness

On a white reflective resin plate having a size of 150 mm×150 mm and athickness of 2 mm, a test piece having a size of 150 mm×150 mm and athickness of 4 mm is placed. On one side of the test piece, a coldcathode tube having a diameter of 2.6 mm and a length of 170 mm isdisposed, and brightness (cd/m²) on 9 spots which are adequatelyscattered on the test piece is measured by the color brightnessphotometer BM-7 of Topcon Corporation. Uneven brightness is determinedfrom the maximum brightness and the minimum brightness out of themeasurement results by use of the following expression.Uneven Brightness (%)=(Minimum/Maximum)×100

In this case, an uneven brightness of 100% implies no uneven brightnessand is optimal brightness.

(10) Curvature Deformation by Absorption of Water

After a test piece whose initial curvature deformation has been measuredis left to stand in constant-temperature constant-humidity equipmentwhose temperature is 50° C. and humidity is 80% RH for 7 days, the testpiece is transferred to an environment whose temperature is 23° C. andhumidity is 50% RH, and the maximum value of curvature deformationthereof is then evaluated by use of a three-dimensional shape measuringinstrument.

Examples A-1 to A-3 and Comparative Examples 1 to 4

To 100 parts by weight of polycarbonate resin (product of TeijinChemicals Ltd.) obtained by use of bisphenol A as a dihydric phenolcomponent and having a viscosity average molecular weight of 15,200,additive compounds were added in parts by weight shown in Table 1 andmixed uniformly. Then, the powders were melt-kneaded by a ventedtwin-screw extruder [KTX-46 of Kobe Steel, Ltd.] at a cylindertemperature of 260° C. under deaeration so as to obtain pellets of theresin compositions. Using the resin composition pellets, variousphysical properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 1.

From these resin composition pellets, optical disk substrates eachhaving a diameter of 120 mm and a thickness of 1.2 mm were molded by useof the injection molding machine MO40D-3H of Nissei Plastic IndustrialCo., Ltd. and a stamper on which grooves each having a depth of 200 nmand a width of 0.2 μm were engraved at an interval of 0.5 μm. Thecylinder temperature and the mold clamping force were fixed at 360° C.and 40 tons, respectively, and the mold temperature was set for eachresin as shown in Table 1. By use of these disk substrates, varioussubstrate properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 1. Stilbene compounds shown in Table1 are as follows.

stilbene: trans-stilbene of Tokyo Kasei Kogyo Co., Ltd. 4,4 dimethylstilbene: 4,4-dimethyl-trans-stilbene of Tokyo Kasei Kogyo Co., Ltd.TABLE 1 Ex. A-1 Ex. A-2 Ex. A-3 C. Ex. 1 C. Ex. 2 C. Ex. 3 C. Ex. 4 Kindof Additive Stilbene Stilbene 4,4 dimethyl — Glass m-terphenyl Biphenylstilbene Fibers Added Amount (wt %) 2 5 5 0 10 5 5 Glass Transition 126114 110 142 142 119 124 Temperature Tg (° C.) Water Absorption (%) 0.220.19 0.20 0.32 0.32 0.20 0.23 Flexural Modulus (MPa) 2,800 3,000 3,1002,300 3,700 2,810 2,810 Mold Temperature Tm₀ 109 97 93 125 125 102 107(° C.) ΔT(° C.)* 17 17 17 17 17 17 17 Initial R-Tilt (deg) 0.08 0.070.07 0.09 0.28 0.07 0.07 ΔR-Tilt max (deg) 0.69 0.52 0.53 0.92 0.95 0.590.75 Transfer Rate (%) 100 100 100 54 12 62 100 Total Light 91 91 91 — —91 91 Transmittance (%) Amount of Deposit on A B B — — B D MoldEx.: Example,C. Ex.: Comparative Example*ΔT = difference between glass transition temperature and moldtemperature = Tg − Tm₀

Examples B-1 to B-3

To 100 parts by weight of polycarbonate resin (product of TeijinChemicals Ltd.) obtained by use of bisphenol A as a dihydric phenolcomponent and having a viscosity average molecular weight of 15,200,additive compounds were added in parts by weight shown in Table 2 andmixed uniformly. Then, the powders were melt-kneaded by a ventedtwin-screw extruder [KTX-46 of Kobe Steel, Ltd.] at a cylindertemperature of 260° C. under deaeration so as to obtain pellets of theresin compositions. Using the resin composition pellets, variousphysical properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 2.

From these resin composition pellets, optical disk substrates eachhaving a diameter of 120 mm and a thickness of 1.2 mm were molded by useof the injection molding machine MO40D-3H of Nissei Plastic IndustrialCo., Ltd. and a stamper on which grooves each having a depth of 200 nmand a width of 0.2 μm were engraved at an interval of 0.5 m. Thecylinder temperature and the mold clamping force were fixed at 360° C.and 40 tons, respectively, and the mold temperature was set for eachresin as shown in Table 2. By use of these disk substrates, varioussubstrate properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 2. A diphenyl carbonate compoundand/or a phenyl benzoate compound shown in Table 2 are as follows.

diphenyl carbonate: product of Teijin Chemicals Ltd. phenyl benzoate:product of Teijin Chemicals Ltd. TABLE 2 Ex. B-1 Ex. B-2 Ex. B-3 Kind ofAdditive Compound Diphenyl Diphenyl Phenyl Carbonate Carbonate BenzoateAdded Amount [wt %] 2 5 5 Glass Transition 134 125 128 Temperature Tg [°C.] Water Absorption [%] 0.23 0.19 0.20 Flexural Modulus [MPa] 2,6102,890 2,870 Total Light Transmittance 91 91 90 [%] Mold Temperature Tm₀[° C.] 117 108 111 ΔT(° C.)* 17 17 17 Initial T-Tilt [deg] 0.09 0.060.06 ΔT-Tilt [deg] 0.67 0.53 0.55 Transfer Rate [%] 100 100 100 Amountof Deposit on Mold A B BEx.: Example*ΔT = difference between glass transition temperature and moldtemperature = Tg − Tm₀

Examples C-1 to C-3

To 100 parts by weight of polycarbonate resin (product of TeijinChemicals Ltd.) obtained by use of bisphenol A as a dihydric phenolcomponent and having a viscosity average molecular weight of 15,200,additive compounds were added in parts by weight shown in Table 3 andmixed uniformly. Then, the powders were melt-kneaded by a ventedtwin-screw extruder [KTX-46 of Kobe Steel, Ltd.] at a cylindertemperature of 260° C. under deaeration so as to obtain pellets of theresin compositions. Using the resin composition pellets, variousphysical properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 3.

From these resin composition pellets, optical disk substrates eachhaving a diameter of 120 mm and a thickness of 1.2 mm were molded by useof the injection molding machine MO40D-3H of Nissei Plastic IndustrialCo., Ltd. and a stamper on which grooves each having a depth of 200 nmand a width of 0.2 μm were engraved at an interval of 0.5 μm. Thecylinder temperature and the mold clamping force were fixed at 360° C.and 40 tons, respectively, and the mold temperature was set for eachresin as shown in Table 3. By use of these disk substrates, varioussubstrate properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 3. Diphenyl sulfone compounds and/orphenyl sulfonic acid phenyl ester shown in Table 3 are as follows.

-   diphenyl sulfone: diphenyl sulfone of Tokyo Kasei Kogyo Co., Ltd.-   difluorodiphenyl sulfone: 4,4-difluorodiphenyl sulfone of Tokyo    Kasei Kogyo Co., Ltd.

phenyl sulfonic acid phenyl ester: phenyl sulfonic acid phenyl ester ofTokyo Kasei Kogyo Co., Ltd. TABLE 3 Ex. C-1 Ex. C-2 Ex. C-3 Kind ofAdditive Diphenyl Difluorodiphenyl Phenyl Compound Sulfone SulfoneSulfonic Acid Phenyl Ester Added Amount (wt %) 5 5 5 Glass Transition127 124 118 Temperature Tg (° C.) Water Absorption (%) 0.20 0.19 0.22Flexural Modulus (MPa) 3,000 3,100 2,850 Total Light 91 91 90Transmittance (%) Mold Temperature Tm₀ 110 107 101 (° C.) ΔT(° C.)* 1717 17 Initial R-Tilt (deg) 0.08 0.06 0.07 ΔR-Tilt (deg) 0.59 0.54 0.63Transfer Rate (%) 100 100 100 Amount of Deposit A A A on MoldEx.: Example*ΔT = difference between glass transition temperature and moldtemperature = Tg − Tm₀

Examples D-1 to D-3

To 100 parts by weight of polycarbonate resin (product of TeijinChemicals Ltd.) obtained by use of bisphenol A as a dihydric phenolcomponent and having a viscosity average molecular weight of 15,200,additive compounds were added in parts by weight shown in Table 4 andmixed uniformly. Then, the powders were melt-kneaded by a ventedtwin-screw extruder [KTX-46 of Kobe Steel, Ltd.] at a cylindertemperature of 260° C. under deaeration so as to obtain pellets of theresin compositions. Using the resin composition pellets, variousphysical properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 4.

From these resin composition pellets, optical disk substrates eachhaving a diameter of 120 mm and a thickness of 1.2 mm were molded by useof the injection molding machine MO40D-3Hof Nissei Plastic IndustrialCo., Ltd. and a stamper on which grooves each having a depth of 200 nmand a width of 0.2 μm were engraved at an interval of 0.5 μm. Thecylinder temperature and the mold clamping force were fixed at 360° C.and 40 tons, respectively, and the mold temperature was set for eachresin as shown in Table 4. By use of these disk substrates, varioussubstrate properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 4. Diphenyl ether compounds shown inTable 4 are as follows.

-   diphenyl ether: product of Wako Pure Chemical Industries, Ltd.

dimethoxydiphenyl ether: product of Teijin Chemicals Ltd. TABLE 4 Ex.D-1 Ex. D-2 Ex. D-3 Kind of Additive Diphenyl Diphenyl DimethoxydiphenylCompound Ether Ether Ether Added Amount [wt %] 2 5 5 Glass Transition135 127 130 Temperature Tg [° C.] Water Absorption [%] 0.20 0.17 0.15Flexural Modulus [MPa] 2,700 3,100 3,400 Total Light Transmittance 91 9190 [%] Mold Temperature 118 110 113 Tm₀ [° C.] ΔT(° C.)* 17 17 17Initial T-Tilt [deg] 0.09 0.06 0.06 ΔT-Tilt [deg] 0.63 0.48 0.50Transfer Rate [%] 100 100 100 Amount of Deposit C C C on MoldEx.: Example*ΔT = difference between glass transition temperature and moldtemperature = Tg − Tm₀

Examples E-1 to E-4

To 100 parts by weight of polycarbonate resin (product of TeijinChemicals Ltd.) obtained by use of bisphenol A as a dihydric phenolcomponent and having a viscosity average molecular weight of 15,200,additive compounds were added in parts by weight shown in Table 5 andmixed uniformly. Then, the powders were melt-kneaded by a ventedtwin-screw extruder [KTX-46 of Kobe Steel, Ltd.] at a cylindertemperature of 260° C. under deaeration so as to obtain pellets of theresin compositions. Using the resin composition pellets, variousphysical properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 5.

From these resin composition pellets, optical disk substrates eachhaving a diameter of 120 mm and a thickness of 1.2 mm were molded by useof the injection molding machine MO40D-3H of Nissei Plastic IndustrialCo., Ltd. and a stamper on which grooves each having a depth of 200 nmand a width of 0.2 μm were engraved at an interval of 0.5 μm. Thecylinder temperature and the mold clamping force were fixed at 360° C.and 40 tons, respectively, and the mold temperature was set for eachresin as shown in Table 5. By use of these disk substrates, varioussubstrate properties were evaluated by the above methods. The results ofthe evaluations are shown in Table 5. A benzophenone compound,diphenylethane dione compound or dibenzyl compound shown in Table 5 isas follows.

-   benzophenone: benzophenone of Wako Pure Chemical Industries, Ltd.-   diphenylethane dione: diphenylethane dione (benzyl) of Wako Pure    Chemical Industries, Ltd.

dibenzyl: dibenzyl of Tokyo Kasei Kogyo Co., Ltd. TABLE 5 Ex. E-1 Ex.E-2 Ex. E-3 Ex. E-4 Kind of Additive Compound Benzophenone BenzophenoneDiphenylethane Dibenzyl Dione Added Amount [wt %] 2 5 5 5 GlassTransition 134 128 128 115 Temperature Tg [° C.] Water Absorption [%]0.24 0.20 0.21 0.19 Flexural Modulus [MPa] 2,630 2,940 2,970 3,030 TotalLight Transmittance 91 91 90 90 [%] Mold Temperature Tm₀ [° C.] 117 111111 98 ΔT(° C.)* 17 17 17 17 Initial T-Tilt [deg] 0.10 0.07 0.08 0.07ΔT-Tilt [deg] 0.72 0.58 0.60 0.51 Transfer Rate [%] 100 100 100 100Amount of Deposit on Mold B B B CEx.: Example*ΔT = difference between glass transition temperature and moldtemperature = Tg − Tm₀

Examples F-1 to F-9 and Comparative Examples 5 to 7

To 100 parts by weight of polycarbonate resin (product of TeijinChemicals Ltd.) obtained by use of bisphenol A as a dihydric phenolcomponent and having a viscosity average molecular weight of 15,200,additive compounds shown in Table 6 were added in an amount of 5 partsby weight, and they were mixed uniformly. Then, the powders weremelt-kneaded by a vented twin-screw extruder [KTX-46 of Kobe Steel,Ltd.] at a cylinder temperature of 260° C. under deaeration so as toobtain pellets of the resin compositions.

From these resin composition pellets, light guide plate test pieces eachhaving a size of 150 mm×150 mm and a thickness of 4 mm were molded byuse of the injection molding machine IS-150EN of TOSHIBA MACHINE CO.,LTD. and a mold having pits and projections shown in FIG. 1 in a cavity.The cylinder temperature was set at 320° C., and the mold temperaturewas set for each resin as shown in Table 6. By use of these test pieces,various properties as light guide plates were evaluated. The results ofthe evaluations are shown in Table 6. TABLE 6 Curvature Deformation MoldUneven by Water Name of Additive Temperature Brightness Absorption No.Compound (° C.) (%) (mm) Ex. F-1 Stilbene 97 89 1.33 Ex. F-2 DiphenylCarbonate 108 88 1.40 Ex. F-3 Phenyl Benzoate 111 88 1.40 Ex. F-4Diphenyl Sulfone 110 87 1.52 Ex. F-5 Phenyl Sulfonic Acid 101 87 1.67Phenyl Ester Ex. F-6 Diphenyl Ether 110 86 1.29 Ex. F-7 Benzophenone 11188 1.49 Ex. F-8 Diphenylethane Dione 111 88 1.52 Ex. F-9 Dibenzyl 98 881.32 C. Ex. 5 — 125 39 2.54 C. Ex. 6 m-terphenyl 102 41 1.59 C. Ex. 7Biphenyl 107 88 2.02Ex.: Example,C. Ex.: Comparative Example

According to the present invention, there can be provided an opticalrecording medium molded from a polycarbonate resin compositioncontaining a specific additive compound, particularly an optical disksubstrate which allows the shape of a stamper to be transferred thereonwith high precision and hardly undergoes warpage caused by environmentalchanges as a high density recording medium, and a light guide platewhich has little uneven brightness and hardly undergoes warpage.

1. An optical disk substrate which comprises a resin compositioncomprising 0.1 to 20 parts by weight of compound represented by thefollowing formula (I):

wherein X represents:

R¹ and R² independently represent a hydrogen atom, a halogen atom, analkyl group or an alkoxy group having 1 to 8 carbon atoms, n and mindependently represent an integer of 1 to 3, and Q¹ and Q²independently represent a hydrogen atom, a chlorine atom, a bromineatom, a cyano group or an alkyl group having 1 to 8 carbon atoms, basedon 100 parts by weight of polycarbonate resin.
 2. The substrate of claim1, wherein the compound represented by the formula (I) is a compoundwherein X is represented by one of the following formulae:

(wherein Q¹ and Q² are the same as defined above.)
 3. The substrate ofclaim 1, wherein the compound represented by the formula (I) is acompound wherein X is represented by the following formula:

(wherein Q¹ and Q² are the same as defined above.)
 4. The substrate ofclaim 1, wherein the resin composition comprises the compoundrepresented by the formula (I) in an amount of 0.5 to 10 parts by weightbased on 100 parts by weight of the polycarbonate resin.
 5. Thesubstrate of claim 1, wherein the polycarbonate resin is a polycarbonateresin having a viscosity average molecular weight of 10,000 to 30,000,6. The substrate of claim 1, wherein the polycarbonate resin is apolycarbonate resin obtained by use of 2,2-bis(4-hydroxyphenyl)propaneas a dihydric phenol component.
 7. The substrate of claim 1, wherein adistance between grooves or pits is 0.1 to 0.8 μm.
 8. The substrate ofclaim 1, wherein the optical depth of a groove or pit is λ/8n to λ/2n,when the wavelength of laser light used for recording and reproductionis λ and the refractive index of the substrate is n.
 9. An opticalrecording medium having a recording surface formed on the uneven surfaceof the optical disk substrate of claim
 1. 10. A light guide plate whichcomprises a resin composition comprising 0.1 to 20 parts by weight ofcompound represented by the following formula (I):

wherein X represents:

R¹ and R² independently represent a hydrogen atom, a halogen atom, analkyl group or an alkoxy group having 1 to 8 carbon atoms, n and mindependently represent an integer of 1 to 3, and Q” and Q²independently represent a hydrogen atom, a chlorine atom, a bromineatom, a cyano group or an alkyl group having 1 to 8 carbon atoms, basedon 100 parts by weight of polycarbonate resin.
 11. The light guide plateof claim 10, wherein the compound represented by the formula (I) is acompound wherein X is represented by one of the following formulae:

(wherein Q¹ and Q² are the same as defined above.)
 12. The light guideplate of claim 10, wherein the compound represented by the formula (I)is a compound wherein X is represented by the following formula:

(wherein Q¹ and Q² are the same as defined above.)
 13. The light guideplate of claim 10, wherein the resin composition comprises the compoundrepresented by the formula (I) in an amount of 0.5 to 10 parts by weightbased on 100 parts by weight of the polycarbonate resin.
 14. The lightguide plat of claim 10, wherein the polycarbonate resin is apolycarbonate resin having a viscosity average molecular weight of10,000 to 30,000,
 15. The light guide plate of claim 10, wherein thepolycarbonate resin is a polycarbonate resin obtained by use of2,2-bis(4-hydroxyphenyl)propane as a dihydric phenol component.
 16. Aliquid crystal display having the light guide plate of claim 10 as abacklight source.
 17. A resin composition comprising 0.1 to 20 parts byweight of compound represented by the following formula (I):

wherein X represents:

R¹ and R² independently represent a hydrogen atom, a halogen atom, analkyl group or an alkoxy group having 1 to 8 carbon atoms, n and mindependently represent an integer of 1 to 3, and Q¹ and Q²independently represent a hydrogen atom, a chlorine atom, a bromineatom, a cyano group or an alkyl group having 1 to 8 carbon atoms, basedon 100 parts by weight of polycarbonate resin.
 18. The composition ofclaim 17, wherein the compound represented by the formula (I) is acompound wherein X is represented by one of the following formulae:

(wherein Q₁ and Q₂ are the same as defined above.)
 19. The compositionof claim 17, wherein the compound represented by the formula (I) is acompound wherein X is represented by the following formula:

(wherein Q¹ and Q² are the same as defined above.)
 20. The compositionof claim 17, wherein the resin composition comprises the compoundrepresented by the formula (I) in an amount of 0.5 to 10 parts by weightbased on 100 parts by weight of the polycarbonate resin.
 21. Thecomposition of claim 17, wherein the polycarbonate resin is apolycarbonate resin having a viscosity average molecular weight of10,000 to 30,000,
 22. The composition of claim 17, wherein thepolycarbonate resin is a polycarbonate resin obtained by use of2,2-bis(4-hydroxyphenyl)propane as a dihydric phenol component.
 23. Amolded article formed of the resin composition of claim 17.